A medical instrument of this kind is known from U.S. Pat. No. 5,766,196.
Medical instruments with a bendable end of the shaft provide the operator with considerably more degrees of freedom of handling in the area of the distal end of the instrument.
In instruments with a rigid shaft, which are mainly used for minimally invasive interventions, this affords the possibility of using the instrument to perform manipulations, within a cavity, that lie outside the longitudinal axis of the shaft.
In the case of flexible shafts, it is possible for these to be introduced into the body through body channels, for example the bronchi, the esophagus or the intestine, and, by additional bending of the distal end of the shaft, the abovementioned additional degrees of freedom of handling are permitted.
The manipulations are of many types. For example, it is possible to perform gripping or dissecting procedures, visual inspections on their own or combined with the aforementioned procedures, coagulation procedures and the like.
To control the bending movement of the shaft, a bend control mechanism is provided that comprises control wires which, in the bendable area of the shaft, are fastened at sites on either side of the central longitudinal axis of the shaft. By pulling one control wire and pushing another control wire, the curving or bending of the shaft can be triggered. At the proximal end, the control wires are mounted on a disc-shaped or drum-shaped body and are fixed there. Turning this body results in one control wire being pulled and the other control wire being pushed.
To turn the drum, the latter is connected to a pivotable control element which can be pivoted to and fro using, for example, a finger of the hand that is holding the medical instrument.
When performing the manipulations, it is desirable for the bendable shaft to remain in defined bent positions, for which purpose a locking mechanism is provided.
In the instrument mentioned in U.S. Pat. No. 5,766,196, this is achieved by the fact that the drum has radially outwardly pretensioned locking pins which engage in hollows or recesses, in the extreme end positions of the bending movement, in order to hold the bent shaft in these positions. In one embodiment, several such locking positions are arranged circumferentially, such that the bent area of the shaft can be locked in numerous bent positions. It is further mentioned in this document that the control wires can be held in a desired position in the bendable area by being held by a resistance force, possibly with a braking mechanism.
It is the object of the present invention is to develop a medical instrument of the type mentioned at the outset in such a way that the bendable portion of the shaft can be locked in any desired position, this being permitted by a safe and ergonomically actuated control mechanism.